(19)

(11)

EP 2 480 744 A2

(12)

(88) Date of publication A3: 14.07.2011 (43) Date of publication: 01.08.2012 Bulletin 2012/31 (21) Application number: 10818003.5 (22) Date of filing: 21.09.2010

(51) International Patent Classification (IPC):  E21B 6/06(2006.01) E21B 3/00(2006.01) E21B 44/00(2006.01) (86) International application number: PCT/US2010/049575 (87) International publication number: WO 2011/035280 (24.03.2011 Gazette 2011/12)

(84) Designated Contracting States: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK SM TR (30) Priority: 21.09.2009 US 244335 P (71) Applicant: National Oilwell Varco, L.P. Houston, Texas 77036 (US)	(72) Inventors: MEBANE III, Robert, Eugene Austin, Texas 78717 (US) FLORENCE, Frederick, Ray Austin, Texas 78751 (US) (74) Representative: Freeman, Avi  Beck Greener Fulwood House 12 Fulwood Place London WC1V 6HR London WC1V 6HR (GB)